Conducting polymerizations under continuous-flow conditions affords distinct advantages over batch experimentation and has increasingly been employed by the research community for chain-growth polymerizations to accelerate material discovery and to finely tune material properties. This work now expands on the reported advances by demonstrating the utility of continuous flow for polyaddition reactions of polyurethanes (PUs). Various reactor configurations enable the on-demand organocatalytic one-step synthesis of linear PUs with tailored soft-to-hard segment ratios in 3-5 min at room temperature. In-line analytics is implemented for real-time process monitoring and to develop process control mechanisms, increasing the control over monomer conversion and material quality and minimizing batch-to-batch variations. The reported strategies thus provide a guideline for the straightforward preparation of libraries of commercially relevant PU materials.